The goal of these studies are to develop improved methods for detecting and treating malignancies. Our group performs pre-clinical evaluation of antibodies that appear to be promising on initial screening by various laboratories in the NCI and develops these for clinical use. After radiolabeling the antibodies quality control testing is performed by our chemistry staff. They are then administered under the supervision of a Nuclear Medicine Physician and an assistant in the Nuclear Medicine Department Serial blood samples, urine's, and often bone marrow or tumor biopsies are obtained to evaluate the distribution of the MoAb in the body. We are collaborating in clinical trials with Dr. Pastan's group and the Medicine Branch using radiolabeled B3 Monoclonal Antibody (MoAb). This antibody is now undergoing testing in a Phase I imaging and therapy trial. Initial imaging studies in 6 patients with colorectal cancer show localization in metastatic sites. This study will continue to accrue patients for imaging and therapy. We are continuing a radioimmunotherapy program of patients with adult T- cell leukemia in collaboration with Dr. Thomas Waldmann's laboratory using In-111 and Y-90 humanized anti-Tac MoAb. The antibody shows good localization and prolonged retention in sites of disease. Although our experience is limited we have not seen significant problems with human anti-human antibody responses. Because of the tumor responses observed thus far with Y-90 humanized anti-Tac this study will continue to accrue patients. We have also started a radioimmunotherapy program of patients with cutaneous T-cell lymphoma using the same antibody.